The invention relates to an apparatus for producing propellant charge powder in the form of strands with axially parallel channels in a press with at least one cavity which, in its strand-forming area, has a plurality of needles for shaping the channels.
Strand-like propellant charge powder is discontinuously produced in pot presses, whose base can contain a plurality of cavities. This leads to several short cylindrical members made from propellant charge powder. Increasing importance is being attached to the continuous production of strands, which can be cut to any desired length. These are produced by means of twin-shaft screw extruders, rotating in the same or opposite directions (DE-OS No. 30 44 577), having in alternating arrangement screw-like conveying segments and steadying zones in a clearly defined arrangement.
A reduced internal diameter mould head is arranged at the extruder outlet side and forms the plasticized propellant charge powder into a strand. The mould head also carries needles which project into the bore of the shaping part and form the channels in the strand.
In order to ensure completely satisfactory burn-up and ballistics, it is necessary on the one hand for the diameter of the individual channels to be closely toleranced and on the other for their arrangement within the strand to be absolutely symmetrical, i.e, the reciprocal spacing of the channels, as well as the spacing between each channel and the centre and from the outer periphery of the strand must be absolutely identical. In connection with presses of all types, it has been found that these requirements concerning the geometry of the channels can frequently not be satisfied. Thus, channel diameter fluctuations occur, which necessarily lead to errors in the overall geometry.